Abstract: This invention relates to apparatus for automatically tracing patterns under the control of a program recorded in a computer. Said apparatus comprises means for initially recording the pattern in a liquid crystal cell by a known method under the control of said computer, and means for projecting the pattern thus recorded onto a photosensitive surface which records it on a reduced scale. It may also be projected on a large scale onto a monitor screen.

Abstract: The method relates to the production of a very thin insulating or weakly-doped layer in the immediate neighborhood of a highly-doped layer within the body of a semiconductor structure designed to operate in the microwave range. For instance a P.sup.+ I N.sup.+ structure is obtained in an N.sup.+ -doped gallium arsenide substrate, by implanting a P.sup.+ - layer using beryllium ions. An insulating layer is spontaneously formed between the highly-doped layers. Using beryllium, the thickness is effectively of the order of one-tenth of a micron. In another example, an avalanche diode of high efficiency, made of gallium arsenide for microwave operation, having a P.sup.+ N.sup.- N.sup.+ N N.sup.+ structure is obtained wherein the layer N.sup.- is the thin weakly-doped layer in the immediate neighborhood of a highly-doped layer (N.sup.+), which is substantially as thin as the N.sup.- layer in this particular case.

Abstract: A Gunn diode comprises deposited in succession on the active zone of gallium arsenide of type N: a first layer of the same material having the same type of conductivity but very strongly doped, and a second layer of amorphous germanium in which is developed a tunnel effect. A metallic deposit covering this second layer serves as cathode contact.